<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <style>
    .container {
      display: flex;
      width: 100%;
    }

    .main {
      flex: 1;
      background: #bbf;
    }

    .side-bar {
      width: 300px;
      height: 500px;
      background: #3ca;
    }

    footer {
      height: 100px;
      margin-top: 2em;
      background: #666;
    }
  </style>
</head>
<body>
  <div class="container">
    <div class="main"></div>
    <div class="side-bar"></div>
  </div>
  <footer></footer>
</body>
</html>
